After a heavy rainstorm, you may notice something puzzling:
One street has standing water, while a nearby street stays relatively dry.
One intersection floods regularly, while another drains quickly.
If the entire area received the same rainfall, why does flooding happen in some locations and not others?
The answer often comes down to how water moves across the landscape. Elevation, drainage patterns, stormwater infrastructure, and even small changes in terrain all influence where water collects during a storm.
Water Always Flows Downhill
Stormwater follows the same basic rule as rivers and streams:
Water moves from higher elevations to lower elevations.
Even in areas that appear flat, there are subtle differences in elevation that influence how runoff travels.
During a storm, water naturally flows toward:
- Low spots in streets
- Ditches and swales
- Storm drains
- Ponds and waterways
When more water arrives than an area can drain immediately, temporary ponding may occur.
Some Areas Are Designed to Collect Water
Not every low area is a problem.
In many communities, certain locations are intentionally designed to temporarily store stormwater during larger rain events.
Examples include:
- Roadside ditches
- Drainage channels
- Detention basins
- Low areas near stormwater ponds
These features help reduce flooding elsewhere by providing space for water to collect until it can move downstream.
Temporary standing water in these locations is often part of the system’s intended function.
Why Storm Drains Are Not Everywhere
A common question is:
“Why isn’t there a storm drain right here?”
Stormwater systems are designed to balance performance, maintenance, and cost.
Engineers evaluate:
- Drainage area size
- Street elevations
- Expected runoff volumes
- Existing ditches and channels
- Long-term maintenance requirements
As a result, storm drains are located where they can provide the greatest benefit rather than at every low spot.
Streets Can Become Part of the Stormwater System
During intense rainfall, streets often help convey water to storm drains and drainage channels.
This may seem unusual, but streets are frequently designed to serve as temporary flow paths during larger storms.
When rainfall exceeds the capacity of nearby inlets or pipes:
- Water collects on the surface.
- Streets direct water toward drainage structures.
- The stormwater system gradually catches up as rainfall decreases.
This is one reason standing water often disappears shortly after a storm ends.
Ditches, Pipes, and Culverts All Work Together
Different parts of the community may use different drainage approaches.
Some areas rely primarily on:
- Underground storm sewers
- Storm drains and inlets
Others rely more heavily on:
- Roadside ditches
- Open channels
- Culverts beneath roads and driveways
Each system has advantages and limitations.
Water may drain differently from one neighborhood to another depending on the infrastructure serving that area.
Debris Can Make Flooding Worse
Even well-designed systems can be affected by blockages.
Common causes include:
- Leaves
- Grass clippings
- Trash
- Sediment buildup
Blocked inlets and culverts reduce the amount of water that can enter the stormwater system, increasing the likelihood of localized flooding.
Keeping drainage paths clear helps water move more efficiently during storms.
What Residents Can Do
Residents can help reduce localized flooding by:
- Keeping leaves and grass clippings out of streets
- Avoiding the placement of debris near storm drains
- Reporting damaged or blocked inlets
- Maintaining drainage around their property
- Directing downspouts away from paved surfaces when possible
Small actions throughout the community can help improve drainage during storm events.
Why It Matters
Flooding is not always caused by a problem with the stormwater system.
Often, it reflects how water naturally moves across the landscape.
Differences in elevation, drainage infrastructure, land use, and storm intensity all influence where water collects during and after a storm.
Understanding these factors helps explain why one street may experience temporary flooding while another remains dry—even during the same rainfall event.
By understanding how local drainage works, residents can better appreciate the role of stormwater infrastructure and help keep the system functioning effectively.
Our Water, Our Responsibility.